The present invention relates to orthopedic bandages which are used to form casts for immobilizing and supporting parts of the body to permit undisturbed healing. More specifically, the invention relates to plaster of Paris containing compositions and carrier materials therefor, which upon activation by wetting, are very soft and conformable, permitting the formation of a smooth, aesthetically pleasing cast; and which exhibit a high green strength permitting early ambulation.
Orthopedic bandages have heretofore been made by coating a flexible carrier or backing with a settable composition. The carrier or backing material generally has been of woven gauze. The settable composition has been of the kind which can be activated by some solvents, heat or irradiation. The bandage is usually in a strip form, wound into a roll or precut to the desired shape. Some bandages are activated just prior to application while others can be cured in place on the body member.
It is important that an orthopedic bandage be soft and conformable to the body member so that a smooth, comfortable cast is formed without ridges or wrinkles which on curing does not create pressure points next to the skin. It is also important that the cast forming material cures rapidly enough and reaches sufficient strength to permit early ambulation.
It has been observed that a low count woven fabric, employed as a carrier for settable compositions, is quite satisfactory for general purpose orthopedic bandages. However, its lack of conformity is a considerable disadvantage when wrapped over uneven surfaces. Also, on application the edge threads tend to become detached from the bandage due to raveling, which interferes with obtaining a smooth and uniform wrap. This lack of conformity can be overcome by the use of elastic warp stretch yarn constructions, some of which are fully conformable. However, they are expensive to manufacture and their elastic properties are difficult to control. Furthermore, some edge threads still ravel and short threads come loose during bandage application.
Other backing materials, such as foam, paper and nonwoven fabrics have also been tried without much success primarily because of their insufficient strength either during the manufacturing process or on application. Efforts to improve strength by increasing their thickness resulted in high bulk and poor lamination of the cast.
Another disadvantage of some cast-forming materials is their insufficient early cast strength which necessitates patients to remain relatively motionless for a substantial length of time. Cast strength and especially early cast strength depend on both the backing material and the settable composition employed and also on the nature of the coating or impregnation of the backing by the settable composition.
Attempts to provide for high early cast strength in an orthopedic bandage, hereafter referred to as "green strength" (as measured one hour after cast application), together with good conformability have proved largely unsuccessful.
It is, therefore, a principle object of the invention to provide a cast-forming material that possesses high green strength thereby permitting early ambulation of the patient. It is a general object of the present invention to provide an orthopedic bandage which is highly conformable and which can be applied over uneven surfaces of the body without the danger of creating pressure points on the skin. Concomitantly, it is also an object to provide an orthopedic bandage that does not suffer the disadvantage of raveling during the wrapping procedure. A still further object is to prepare a cast-forming material with a carrier or backing strong enough to withstand stresses to which it may be subjected during the coating process.